Submerged arc welding - what is it?

Automatic submerged arc welding technology

Any practicing welder knows that oxygen has a negative effect on the quality and durability of the weld. Oxygen entering the weld pool promotes increased oxidation and causes cracks. There are many ways to get rid of this problem: from special metal processing to the use of special components, for example, fluxes.

One of the most popular methods of high-quality joining of metals is automatic submerged arc welding. It can be used to weld difficult metals such as copper, aluminum and stainless steel. Automatic welding speeds up and simplifies work, and the flux performs a protective function. In this article, we will briefly explain what automatic submerged arc welding is and what is the technique of automatic submerged arc welding.

general information

Automatic submerged arc welding is a technology whose essence is no different from classical arc welding. The metal melts due to the high temperature that is formed due to the electric arc. Below is a diagram of automatic submerged arc welding.

The only difference between automatic welding and any other is that most of the processes are performed not manually, but using special machines. For example, wire feeding and arc movement. Well, in our particular case, all these operations are performed under a layer of flux applied to the surface of the metal.

Application area

Automatic submerged arc surfacing is used in many fields. With its help, you can organize fast large-scale production, including conveyor production. For this reason, this technology is indispensable in the assembly of ships, the production of large-sized pipes and tanks for the oil refining industry. Automatic welding provides high quality seams, which is why it has gained respect in such critical industries.

The role of flux

With automatic welding everything is clear. But what about flux? What it is?

Flux is a special substance (can be produced in the form of powder, granules, pastes and liquids) with positive properties. Fluxes are fed in a thick layer directly into the welding zone, protecting it from the negative effects of oxygen. Flux also protects the metal itself, promotes stable arc burning, reduces the likelihood of metal spattering, and even changes the chemical composition of the weld if necessary.

Types of fluxes used

Before you carry out submerged arc welding, it would be nice to know what types there are. First of all, all fluxes are divided according to their intended purpose. They can be used for welding carbon and alloy steels, for high-alloy steels and for non-ferrous metals. This is the first thing you should pay attention to before purchasing flux.

Fluxes can also be fused or ceramic. Their difference is in composition. In most cases, fused flux is used, since it is relatively universal and inexpensive. With its help, you can effectively protect the weld pool from oxygen. But don’t expect any special qualities from the fused flux. If you need truly excellent weld properties, then choose a ceramic flux. It provides excellent quality.

Also, fluxes can be chemically active and chemically passive. Active flux contains acids that can not only protect the metal during welding, but also lead to corrosion. So be sure to remove flux thoroughly after use. Passive fluxes are not used in automatic welding because they do not have sufficient properties for this. Often you will find a passive substance when soldering in the form of wax or rosin.

By the way, about the manufacturers. This is a long-standing debate among all beginners and experienced welders. Some people believe that domestic companies produce inexpensive and effective flux, while others are all for imported components. We will not say unequivocally which is better, we will only say that in practice, both domestic and imported fluxes perform well if the welding technology is followed.

Advantages and disadvantages

Automatic flux welding has many advantages. Its main advantage is the ability to fully automate the welding process. A welder does not even need to know how to weld; it is enough to know how to set up the equipment. Also, this welding method guarantees excellent quality of welded joints, since there is no human factor.

The technology of welding parts by automatic surfacing under a layer of flux also has its disadvantages. Firstly, you can only weld the bottom seams. Also, the parts must be very precisely fitted, because the machine forms a seam in a clearly defined place, and any mistake during joining will lead to defects. In addition, very careful preparation of the metal is required before welding.

Please note that you will not be able to weld metal by weight. The part will need to be fixed on a horizontal surface and the root of the welded joint will need to be pre-welded. Another significant drawback is the high cost of both automatic welding equipment and components.

Now that you know everything, it's time to find out what automatic submerged arc welding technology is.

Welding technology

First of all, before welding, it is necessary to prepare the metal. Each metal has its own preparation, but we will give general recommendations. It is necessary to clean the part from dirt, paint and corrosion. Then you need to thoroughly clean the surface using a wire brush or grinding wheel. Only after the preparatory operations can you start welding.

Submerged arc welding technology is simple due to the fact that many processes are performed not by a person, but by a machine. The master does not need to light the arc, monitor its stability, select the wire feed speed, and so on. All you need to do is set the submerged arc welding modes correctly. Essentially, give the machine a program of action. Below is a table listing the modes of automatic submerged arc welding.

These are automatic submerged arc welding modes for butt joints. Naturally, there are other types of joints, so for them it is necessary to calculate the welding modes. Here we will not touch on this topic, since it is very extensive (there are so many types of compounds, so many formulas), so study this information yourself. There are many calculation methods on the Internet.

The work also uses a special filler wire for submerged arc welding. Its feeding is also automated; you just need to load the reel into the feeding mechanism. We recommend purchasing wire made from the same metal as the part.

Now a little about flux. It is also supplied automatically, only it must first be poured into a special tank. The thickness of the flux layer depends on the thickness of the metal being welded. The thicker the metal, the more flux is needed.

A natural question may arise in your mind: does flux melt? And does it affect the structure of the seam? Yes, of course, flux melts under the influence of temperature. But at the same time, it does not violate the structure of the seam in any way, but only improves it. But at the same time, the frozen flux turns into slag, which must be removed after welding. Leftover unused flux can be reused.

This technology of using flux in automatic welding can significantly increase the speed of work without losing quality.

Instead of a conclusion

Now you know automatic flux welding and what it is. Of course, in addition to automatic welding, there is also manual submerged arc welding, semi-automatic submerged arc welding and mechanized submerged arc welding.

But one article cannot reveal all the nuances of these types of welding, so we are telling you about them gradually. You can find articles on these and many other topics on our website. Share your opinion and experience in the comments.

Craftsmen can tell their secrets of using flux in automatic welding and share their knowledge. Good luck!


Source: https://svarkaed.ru/svarka/vidy-i-sposoby-svarki/tehnologiya-avtomaticheskoj-svarki-pod-flyusom.html

Submerged arc welding - nuances of technology, advantages and disadvantages

In the construction and industrial sectors, submerged arc welding is now actively used to join metals. The high popularity of this technology is explained by the advantages it has.

Submerged arc welding process

GOST 8713-79 on submerged arc welding

Welding, in which the zone of molten metal is protected by flux, was invented quite a long time ago - in the 19th century. This technology was developed by N. Slavyanov, and the first automated welding machine for its implementation and the practical basis for its implementation were created already in 1927 by D. Dulchevsky. Almost immediately after this, automatic submerged arc welding began to be actively introduced into production processes at large domestic industrial and construction enterprises.

Throughout the entire period of existence of this technology, both submerged arc welding itself and the equipment for its implementation have been constantly evolving. The issues of improving the method and technology for its practical implementation were dealt with by leading research institutes of the Soviet Union: Institute of Electric Welding Units of the Soviet Union, Central Research Institute of Heavy Engineering, Institute named after E.O. Paton and others.

Submerged arc welding diagram

The technology of automatic submerged arc welding is regulated in detail by GOST 8713-79. There is also a classification of welding methods under a protective layer of flux, which can be used to join steels and alloys with a nickel and iron-nickel base. GOST 8713-79 distinguishes two such methods: mechanized and automatic submerged arc welding. And these varieties are divided into the following subspecies:

1. mechanized: performed on weight (MF), with a pre-made weld seam (MFsh), using the remaining lining (MFo);
2. automatic: performed on a lining (AFo) and using a flux pad (AFf), with preliminary welding of the weld root (AFk), using the so-called copper slider (AFp), performed in weight (AF), with preliminary welding ( AFsh), welding on flux-copper backing (AFm).

Some types of seams used in submerged arc welding

Also, GOST 8713-79 specifies the types of welded joints obtained using these methods, which can be:

• one-sided type; double-sided; butt one-sided - locking, which can be made with a straight or curved bevel of both edges, with a symmetrical bevel of one edge, with a broken type bevel, without a bevel at all - with subsequent gouging, with flanging and asymmetrical bevel of both edges;
• angular double-sided and single-sided types, in which there may be no bevels, they can be asymmetrical, and also made with flanging;
• lap seams made without bevel, on one or both sides;
• tee seams of two- and one-sided type.

An example of submerged arc welding can be seen in the following video:

GOST 11533-75 lists the requirements for automatic and semi-automatic methods for submerged arc welding of parts made of carbon and low-alloy steels. These welding methods include:

• semi-automatic arc welding performed using a steel backing (Ps); welding of semi-automatic type (P) and semi-automatic with welding seam (PPsh);
• automatic welding performed with a preliminary weld seam (Apsh);
• automatic submerged arc welding performed on a special steel backing.

Submerged arc welding technology

Automatic and mechanized types of welding under a layer of flux differ from traditional technology in that the arc, when performed, does not burn in the open air, but under a layer of bulk substance with a number of special properties, which is called flux.

At the moment the welding arc is ignited, the metal of the part and the electrode, as well as the flux used, begin to melt simultaneously.

As a result of metal and flux vapors formed in the welding zone, a gas cavity is formed, which is filled with the resulting vapors mixed with welding gases.

An example of the appearance of a seam after submerged arc welding

The cavity formed during such welding is limited in its upper part by a layer of molten flux, which performs not only a protective function. The molten metal of the electrode and the part being welded, interacting with the flux, undergoes metallurgical processing, which helps to obtain a high-quality weld.

When the arc is removed from a certain welding zone, the molten flux solidifies, forming a hard crust on the finished seam, which is easily removed after the product has cooled. If automatic submerged arc welding is performed, then unused flux is collected from the surface of the part using a special suction device equipped with automated equipment.

Source: http://met-all.org/obrabotka/svarka/svarka-pod-flyusom.html

Submerged arc welding: what is it, advantages

Submerged arc welding: what is it, advantages

Arc welding is primarily referred to as a process in which two pieces of metal are welded together using an electric arc. It is formed by a power source, which can be direct or alternating current.

An arc is created between the electrodes and the workpiece. One such type of welding is submerged arc welding (SAW), so named because the arc zone, electrode tip, and cast weld are hidden under a layer of granular fusible flux. This is done to protect against air pollution.

SPF can be performed automatically or manually. Some companies use semi-automatic pistols to do this job. Although SPF can work with full automation, people generally do not choose this option.

What are the advantages of submerged arc welding

The arc welding process produces spatter and sparks. And at the same time creates intense ultraviolet radiation and smoke. In the SPF process, such factors are eliminated, since the molten metal is completely covered with a thick layer of flux, which makes it environmentally friendly.

In addition, the suppression of radiation and smoke makes SPF safer than other types of welding. Operators supervising welding are not required to wear protective clothing, but rather wear normal work clothing.

Since submerged arc welding uses electricity, it does not need to be applied under pressure. Due to the high heat generated during the welding process, this method is well suited for welding thick profiles. Read about how to cook channel bars on the website mmasvarka.ru.

Submerged arc welding is particularly famous for its high rate of metal deposition. Thanks to this property, welding provides deep penetration into the weld. Submerged cored wire welding provides better deposition rates than solid wire.

In addition, the concentration of a huge amount of heat allows you to speed up this process. Speeds up to 5 m/min are achieved. The final weld product, the weld metal, is produced with superior quality in uniformity, toughness, corrosion resistance and durability. In addition, the weld shapes have a cleaner appearance and a smoother surface.

One of the biggest problems in welding processes is weld deformation. This occurs as a result of expansion and contraction of the weld metal and adjacent non-ferrous metals. Because SPF uses higher heat concentrations and faster welding times, it can significantly reduce such disturbances.

This welding process can be used both indoors and outdoors. Even in relatively windy areas, submerged arc welding meets absolutely all welding requirements.

Where is submerged arc welding used?

This process is suitable for welding low alloy steel with low tensile strength. It is widely used in the construction of railways, boilers and equipment used to move soil. Submerged arc welding is also commonly used to make cranes, bridge support beams, and the lowest supports for railroad cars and locomotives.

In conclusion, the fusible flux used in SPF remains solid granular throughout the welding process, allowing 50-90% of the flux to be reused.

Source: https://mmasvarka.ru/dugovaya-svarka-pod-flyusom.html

What is submerged arc welding: advantages of technology, varieties, pros and cons

It has long been known that the processes that occur in the weld pool are negatively affected by air. Nowadays, production uses technologies that can eliminate this factor.

Today, manual arc welding, gas-shielded or automatic submerged arc welding is mainly used. The latter option not only allows you to do the job much faster, but also improves the characteristics of the seam.

What is this method?

Flux Welding is a process in which an arc between the work material and the wire burns under granular powder . When exposed to high temperatures, the granules and electrode begin to melt. As a result, an elastic film forms around the weld pool. It protects the molten metal and the arc from adverse effects, and also prevents air from entering.

During cooling, the flux elements are converted into slag, covering the seam. At the end of welding, the deposited crust can be easily removed from the metal mechanically. The remains of the flux layer are collected and used in the future. You can make connections under a loose blanket using different equipment.

Semi-automatic welding

In this case, the master will have to guide the wire and control the protrusion of the electrode. The welding wire is fed automatically. The welder only needs to select the speed, arc voltage power and electrode angle.

Robotic automatic welding

This technology involves submerged arc welding of smooth surfaces and fillet welds. Moreover, the speed and direction of movement of the electrode is determined by the device. The robotic method makes it possible to achieve a strong connection; in addition, it is characterized by speed and high quality of seam application.

, tandem technology has become very common . In this method, two electrodes are parallel to each other in the same plane. Automatic submerged arc welding in tandem improves the quality of the seam. In addition, this method has a minimum weld pool size and instantaneous arc initiation.

Types of fluxes

They are divided into several groups, depending on the metal:

• High alloy steels;
• Non-ferrous alloys and metals;
• Alloy and carbon steels.

Moreover, depending on the production method, the flux can be ceramic or fused . In the first case, ceramic substances are presented that have alloying qualities and an improved seam, and in the second, they have a pumice-like or glassy structure.

Ceramic flux is created by grinding elements, mixing with extrusion, which helps to achieve a homogeneous mass and better grinding, as well as with liquid glass. A similar process using these mixtures is performed if additional alloying of the weld material is required.

Fused flux is produced by sintering the starting materials, with their further granulation.

In addition, fluxes for gas and electric welding are divided according to their chemical composition into the following categories:

• Saline. They contain only fluorides and chlorides. They are used for flux arc welding of slag remelting and active metals;
• Mixed. They are a combination of salt and oxide mixtures. With the help of such fluxes, alloy steels are welded;
• Oxide. Such mixtures are needed for welding low-alloy and fluoride steels. They contain metal oxides with a small content of fluoride compounds.

As you can see, there are quite a lot of different modifications of this material. But it should be remembered that automatic welding is considered successful if the appropriate flux is used.

Basic modes

The most important modes for automatic flux welding are values ​​such as polarity, type and strength of current , arc voltage, speed and size of the electrode wire.

Not so important, but also significant, are such modes as the angle of inclination of the welded edges and the electrode, the size of its extension, the composition of the flux, the preparation of the metal and the type of welded joint.

When selecting the parameters of submerged arc welding modes, the requirements for the size of the weld and geometric shape, the thickness of the edges and the width of the joint are also taken into account.

Before you start welding, you must first select the wire size. It is necessary to proceed from the welded thickness. Then the size of the welding current is selected, and the wire feed speed is determined.

Most often, solid wire with a size of 1–6 mm is used for submerged arc welding. In this case, the current should not exceed 150-2000 A , and the arc voltage - 22-55 V.

Pros and cons of submerged arc welding

In this technology, welding current is supplied to the wire through a mouthpiece. It is located at a short distance from its edge, usually less than 70 mm. Due to this, the electrode cannot overheat, so high currents are used. All this helps to achieve deep penetration and rapid deposition of metal. Moreover, in this way it is possible to weld thicker metal without separating the edges.

Arc welding, performed automatically using submerged arc welding, ensures the consistency of the shape and size of the seam, and also creates uniformity of its chemical composition . Thus, allowing you to obtain a high-quality connection with high stability of its qualities. This welding method allows you to avoid many defects, for example, the occurrence of areas where elements are not fused and undercuts.

During this welding process, metal spattering does not occur, since the weld pool and arc are protected from air. Thanks to this, there is no need to clean the surface of the material from splashes. Submerged arc welding allows you to save energy and welding materials by approximately 30-40%.

The welder performing the work does not have to use protection for the face and eyes, because the emission of harmful gases is much less than during manual welding.

True, automatic submerged arc welding has not only advantages, but also disadvantages. One of them is the fluidity of the flux and molten metal. That is why you can only cook in the lower position, and the deviation of the seam plane from the horizontal should be 10-15° .

If this rule is neglected, various defects may occur. It is because of this that submerged arc welding is not used to fasten rotary annular joints of pipes whose diameter is less than 150 mm. In addition, this method requires more careful assembly of the edges and the use of certain techniques.

Why is flux welding needed?

Works using flux were able at one time to produce a real revolution in the industrial sector. Initially, this technology was intended for processing low-carbon steel . However, nowadays the powder can be used for almost any material, including refractory metals and steels that are difficult to process.

The metallurgical processes occurring during flux welding have made it possible to use semi-automatic and mechanized equipment for the following work:

• Connecting vertical seams. It is carried out with free or forced formation of the seam. The best adhesion strength is achieved with metals 20-30 mm;
• Welding pipes of different diameters. At first they learned how to connect small-diameter pipes using automatic installations, but with the improvement of processing technology, they were able to master a method that allows them to weld large-sized materials;
• Welding circular seams. The difficulty of such work is that you need to hold the weld pool and try to avoid metal spreading. This kind of flux welding is performed on CNC machines. In some situations, manual welding may be necessary.

The implementation of all these works is regulated according to the welding flow chart . For any violations, heavy penalties are imposed.

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Submerged Arc Welding (SAW)

In submerged arc welding, the welding arc burns between the workpiece and the end of the welding wire. As the wire melts, it is automatically fed into the welding zone. The arc is covered with a layer of flux. The welding wire is moved in the direction of welding using a special mechanism (automatic welding) or manually (semi-automatic welding).

Under the influence of the heat of the arc, the base metal and flux melt, and the flux forms an elastic film around the welding zone, isolating this zone from air access. Drops of welding wire metal melted by the arc are transferred through the arc gap into the weld pool, where they are mixed with the molten base metal.

As the arc moves forward, the metal of the weld pool begins to cool, as the heat supply to it decreases. It then hardens to form a seam. When melted, the flux turns into liquid slag, which covers the surface of the metal and remains liquid for some time after the metal has already hardened.

The slag then hardens, forming a slag crust on the weld surface.

One of the variations of this welding method is flux welding. In this case, a significantly smaller thickness of the flux layer is used than in submerged arc welding. The arc burns in conditions of free air access. The molten metal wire when passing through the arc gap does not have slag protection.

The metal of the weld pool and the seam are covered with a thin layer of slag. During submerged arc welding, the metal is much less protected from air than during submerged arc welding. In addition, arc radiation and intense smoke and vapor emissions have a harmful effect on operating personnel.

This welding method is used for welding aluminum and its alloys.

Submerged arc welding equipment: power source characteristics, current type

The industry produces two types of submerged arc welding machines:

1. With a constant feed speed of the electrode wire, independent of the arc voltage (based on the principle of self-regulation of the welding arc) - for welding with wire up to 3 mm
2. With automatic regulation of arc voltage and electrode wire feed speed dependent on it (devices with automatic regulation) - for welding with wire with a diameter of more than 3 mm.

In welding heads with a constant feed speed, when the length of the arc gap changes, the mode is restored due to a temporary change in the melting rate of the electrode due to self-regulation of the arc.

As the arc gap increases (increases in arc voltage), the welding current decreases, which leads to a decrease in the melting rate of the electrode. A decrease in arc length causes an increase in welding current and melting rate.

In this case, power supplies with a rigid current-voltage characteristic are used (see the article Volt-ampere characteristics of the arc).

In welding heads with an automatic arc voltage regulator, a violation of the length of the arc gap causes such a change in the feed speed of the electrode wire (acting on the DC motor), at which the specified arc voltage is restored. In this case, devices with a decreasing current-voltage characteristic are used.

The devices of these two types also differ in the setting of the main parameters to a given mode: welding current and arc voltage. On machines with a constant feed speed, the set value of the welding current is adjusted by selecting the appropriate value for the electrode wire feed speed. The arc voltage is adjusted by changing the open circuit voltage of the external characteristics of the power source.

On machines with automatic regulation, the arc voltage is set on the control panel and is automatically maintained constant during welding. The set value of the welding current is adjusted by changing the slope of the external characteristic of the power source.

Setting other parameters of the welding mode (welding speed, electrode stickout, flux layer height, etc.) is similar for both types of devices and is determined by the design features of a particular device.

Submerged Welding Connection Design

The form of edge preparation for mechanized submerged arc welding is selected depending on the thickness of the products being welded and in accordance with:

• GOST 8713-79 “Seams of welded joints. Automatic and semi-automatic submerged arc welding. Basic types and structural elements"
• GOST 11533-75 “Automatic and semi-automatic submerged arc welding. Welded connections at acute and obtuse angles"
• GOST 16098-70 “Seams of welded joints made of two-layer corrosion-resistant steel”
• GOST 15164-78 “Welded joints and seams. Electroslag welding. Basic types and structural elements."

Application area of ​​submerged arc welding

Mechanized submerged arc welding is one of the main fusion welding methods.

If in the first years of development, submerged arc welding was used only in the manufacture of welded structures from low-carbon steels, now low-alloy, alloyed and high-alloy steels of various classes, and nickel-based alloys are successfully welded. Submerged arc welding of titanium and its alloys has been mastered.

Submerged arc welding is used to weld copper and its alloys, as well as aluminum and aluminum alloys. Products produced by submerged arc welding operate reliably at high temperatures and in deep cold conditions, in aggressive environments, in vacuum and under high pressure conditions.

It is most profitable to use mechanized submerged arc welding in the production of welded structures of the same type that have long seams and are convenient for holding flux. It is more economically feasible to submerged weld metal with a thickness of 1.5 - 2.0 to 60 mm. It is not advisable to weld structures with short seams.

Single or multi-wire submerged arc welding technologies

There are varieties of submerged arc welding, where in some cases it is advisable to use double-arc or multi-arc welding. In this case, the arcs are powered from one source or from a separate source for each arc. When welding with a double (split) electrode, the arcs burning in a common pool are powered from one source. This slightly increases welding productivity by increasing the amount of molten electrode metal.

The electrodes can be positioned in series or perpendicular to the welding direction. With a sequential arrangement, the depth of weld penetration increases slightly, and with a perpendicular arrangement it decreases.

The second option for the location of the electrodes allows welding to be performed with increased gaps between the edges. By changing the distance between the electrodes, you can adjust the shape and size of the seam. It is convenient to use this method during surfacing work.

However, the disadvantage of this method is some instability of the arc.

In double-arc welding, two electrodes are used (in multi-arc welding, several). Arcs can burn into a common or separate weld pool (when the weld metal has already completely crystallized after the first arc). When the arc burns into separate weld pools, both electrodes are usually perpendicular to the plane of the product. By changing the distance between the arcs, you can adjust the thermal cycle of welding, which is important when welding hardening steels.

This scheme allows welding at high speeds, while the use of increased current during single-arc welding leads to non-fusion - undercuts along the edges of the seam. In double-arc welding, the second arc, burning in a separate pool, with an electrode inclined at an angle forward (angle α = 45-60°), partially melts the seam formed by the first arc and forms a widened bead without undercuts.

To power arcs in order to reduce magnetic blast, it is better to use a dissimilar current (for one arc - alternating, for the other - direct).

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Submerged arc welding

A detailed acquaintance with welding work and processes indicates that air has a negative impact on the quality of the connection. The required fastening can be achieved using a protective medium, which includes fluxes or inert gases.

The most common use of fluxes is in industrial conditions, due to the fact that when using this method, a reliable fastening is guaranteed to be formed.

Use implies automatic or semi-automatic mode; some production lines use robotic installations.

Submerged arc welding

What does the use of flux give?

A chemical substance based on many components is called flux. It is used when necessary to comply with standards, to protect metal products from corrosive conditions during subsequent operation.

Welding flux

The main tasks that the substance can solve:

• stable burning of the welding arc;
• improved properties and shapes of the seam;
• providing a weld pool that protects the metal;
• the use of various fasteners allows you to change the composition of the chemical mixture to obtain the required characteristics.

In addition to the above advantages, the main advantage is the ability to create a mechanical joining process. Various chemical compounds are used in automatic lines.

Chemical composition of various brands of flux

Each method has its drawbacks, and the use of flux is no exception:

• work is performed only with the joint in the lower position;
• assembly of parts must comply with the parameters of fitting and edge processing;
• production is carried out only on a rigid support, suspended impact on the material is not possible;
• the cost of auxiliary materials is high, so the method is used in critical structures.

Welding aluminum or other non-ferrous metals is impossible without the use of flux, regardless of the joining method. However, there is a possibility that solid oxide will form and be forced to the surface during the process.

Joining non-ferrous metals by welding involves the use of various compositions. The component part is divided into manganese, low silicon, oxygen-free products. Fused compositions have the structure of pumice, alloying properties exist in ceramic products, improving fastening properties. Components of the main varieties:

• Salt compounds are rich in fluorides and chlorides. With their help, manual argon arc welding is performed using active compounds and slag remelting.
• Oxide mixtures have found their purpose in joining fluoride parts, as well as low-alloy materials. This product is distinguished by its silicon content and has up to ten percent fluoride compounds.
• Mixed products are used for high-alloy steels; the structure is made up of all the elements listed in the first two materials.

Choosing the right flux is quite difficult without the appropriate experience; automatic submerged arc welding requires high-quality material.

The type and characteristics of the composition are determined by the technical documentation.

Submerged arc welding modes for steels

Automated welding is carried out in such a way that the operator only performs debugging of the equipment in the appropriate operating mode. Sequence of actions and technology:

• Flux is automatically supplied to the parts to be joined, the layer height is adjusted in relation to the thickness of the metal, and the product is taken from a specially designated hopper.
• The cassette mechanism feeds the electrode wire, without which the process is impossible.
• The operating speed is selected in such a way that a high-quality weld pool is formed, preventing metal spattering.
• A product with a lower density floats to the surface of the bath, which does not affect the properties of the seam. Unused material is mechanically collected to save money.

The main positive quality is the increased speed through mechanized submerged arc welding. Thanks to this, the method is used by various industries and has proven itself to be a reliable and durable way to connect welded parts.

The seam is made according to several characteristics, and operating modes are selected depending on this. A common type is cold welding, used at low temperatures to join non-ferrous metals.

Each material has a technical specification with permitted welding parameters.

In the absence of instructions, the substance is selected for use using a sample method; it is important to follow some tips:

• A high quality connection can only be achieved with a stable arc. The parameter is adjusted by selecting the speed level of the melting tool and the current strength.
• The speed performance is affected by the degree of wire extension, as well as the alloy composition.
• The current strength directly depends on the depth, and the voltage can be used to adjust the width of the seam.

The mechanism of operation of fluxes during welding

Thus, it is possible to select the required substance as accurately as possible. It is necessary to understand that you should not neglect control, because... The connection may be disrupted during further use.

Equipment for submerged arc welding

At production facilities, an assembly-type stand is used, on which it is possible to fix the elements being processed in a stationary state. The requirement for reliable fastening is especially observed, because During work, the part may shift, resulting in an uneven weld. Often, instead of full-fledged expensive submerged arc welding equipment, mobile heads are used.

Submerged arc welding machine

A trolley equipped with an electric drive and a mechanical welding head is called a tractor. This device is capable of moving along the seam directions or directly to the parts.

Submerged arc welding - modes, features

Anyone familiar with welding processes knows how negatively air affects the quality of the weld. That is why the highest quality connection is considered to be a process that is carried out in an environment of protective materials. Typically, inert gases or fluxes are used for this. Submerged arc welding is not used so often today, especially in domestic conditions.

But in industry, this type of metal welding is used much more often. Moreover, the quality of the seam with this technology is guaranteed to have high quality characteristics. Therefore, when talking about submerged arc welding, it is necessary to understand that this process is semi-automatic or automatic.

In some industrial production, robotic welding using fluxes is installed.

What is welding under protective fluxes

Essentially, this is the same welding process using non-consumable electrodes and filler wire. Only instead of gas, which covers the welding zone, flux is used - a powdery material poured over the junction of two metal workpieces.

At high welding temperatures, the flux melts and releases the same protective gas. In this case, a durable film is formed over the welding zone, protecting it from the negative effects of ambient air. The burnt powder turns into slag, which is easily removed from the welded seam. Remaining flux can be collected and used elsewhere.

But the most important thing is that all positions associated with connecting the joined parts are exactly the same as in the case of using other welding technologies. Namely:

• correct selection of welding mode, which depends on the structure of the metals being joined;
• correct choice of electrode;
• filler wire, which in its properties must correspond to the properties of the base metals;
• competent formation of edges;
• cleaning the ends of parts, degreasing them.

But there is one distinctive feature - the correct choice of flux.

Types of fluxes

As mentioned above, flux for welding is a powder with granule sizes of 0.2-4 mm. Its classification depends on many indicators. But there are basic characteristics that divide it into groups and classes.

According to the production method, welding fluxes are divided into:

• fused: their components are first melted, then granulated, calcined and separated into fractions;
• unfused or ceramic: these are dry ingredients that are mixed with liquid glass, dried, granulated, calcined and separated into fractions.

Manufacturers and experts note the fused version as the best of the two presented.

Separation by chemical composition.

• Oxide fluxes. The powder contains up to 90% metal oxides and the rest is fluoride compounds. This group has subgroups that determine the percentage of a particular oxide. For example, silicon oxide. If it is contained in the flux up to 1%, then such a powder is called silicon-free, if its content is 6-35% - low-silicon and more than 35% - high-silicon. Oxide fluxes are designed for welding low-carbon and fluoride steel workpieces.
• Saline. They do not contain metal oxides; they are based on salts: fluorides and chlorides. This powder is used for welding active metals, for example, titanium.
• Mixed fluxes (salt oxide). They contain both oxides and salts. They are used to join alloyed alloys.

Another characteristic is the activity of fluxes. Essentially, this is the rate of oxidation of the powder when it is heated. This indicator is measured from zero to one and divides fluxes into four categories:

1. Less than 0.1 are passive materials.
2. From 0.1 to 0.3 – inactive.
3. From 0.3 to 0.6 – active.
4. Above 0.6 – highly active.

And one last thing. This is a division based on the structure of the granules. There are three positions: vitreous, pumiceous and cemented. It should be noted that welding with a glassy flux produces a wider weld than with a pumice flux. If a powder with small particles is used, then the seam underneath is deep and narrow with high strength properties.

Useful tips

• The transition of metals (manganese and silicon) into the weld metal is of great importance in submerged arc welding technology. Manganese is transferred faster if the concentration of its oxide (MnO) is greater than that of silicon oxide (SiO2). The lower the flux activity, the faster the transition occurs.
• Pores form in the seams if the flux has not been well dried, if it does not match the properties of the metal of the workpieces being welded and the metal of the filler wire, if there is too much gap between the parts, if the flux layer is insufficient, if its qualities are low.
• Hydrogen has a negative effect on the welding seam. Therefore, it is bound into insoluble compounds using fluxes. This is best done by a powder with a high silicon content and a pumice-like granule shape.
• To prevent cracks from forming in the weld, fluxes with a high content of both silicon and manganese are needed.

Today, double or two-electrode welding is increasingly used in industry, in which the electrodes are located at a distance of less than 20 mm from each other and are powered by a single source of electrical energy. At the same time, they are welded in one zone, forming a single weld pool. The electrodes can be located both in a longitudinal and transverse position.

Double-arc welding is also used, in which consumables are powered from two different sources, and the current on the two rods can be alternating or constant. Or it may be different. The location of the electrodes can be perpendicular to the welding plane or at an angle. By varying the angle of inclination, you can increase or decrease the depth of welding. The width of the seam will change accordingly.

Submerged arc welding can also be carried out when the distance between consumables is increased. In this case, welding will be carried out in parallel in two baths. But the first electrode will serve as a heater for the welding zone, the second will weld it.

With this technology for joining metal workpieces, the electrodes are installed perpendicular to the welding plane.

This method is distinguished by the fact that during welding with two electrodes, hardening areas are not formed both in the weld itself and in the adjacent areas on the main parts.

Submerged Welding Modes

It should be noted that mechanized submerged arc welding differs from manual welding in that it becomes possible to use high-density welding current. It varies in the range of 25-100 A/mm². Accordingly, more current will be used. This is reflected in deep welding of the seam, the ability to weld thick-walled workpieces without forming edges, and increasing the speed of the process itself.

For example, when welding parts with a thickness of 20-40 mm using single-arc manual welding, the process speed is no more than 70 m/hour. Using double-arc welding, you can increase this figure to 300 m/hour. Of course, the current strength is selected mainly based on the diameter of the electrode used. The table shows their relationship with each other.

Electrode diameter, mm	Welding current strength, A
2	200-400
3	300-600
4	400-800
5	700-1000
6	700-1200

It should be added that flux-cored welding technology is also economical. The thing is that the consumption of materials is reduced due to less spattering of metal, for example, in manual welding this figure is 15%, in flux mechanized welding it is less than 3%.

The volume of waste is reduced, cinders and other unpleasant moments are not formed. Conserving heat under flux also makes it possible to save energy. It has already been proven that the reduction in electrical current consumption occurs by up to 40%.

Labor costs, which are usually spent on forming edges and cleaning the seam after welding from scale, splashes and slag, are also reduced.

The only negative is the restriction on the position of the weld pool. You can cook in the lower position using automatic or semi-automatic devices or with a slight tilt within 10-15°.

Be sure to watch the video, which shows how you can submerge weld two metal parts.

Source: https://svarkalegko.com/tehonology/svarka-pod-flyusom.html

Submerged arc welding technology

The principle of working with flux is no different from conventional electric arc welding. The metal also melts under the influence of high heat from the welding arc. But it is automatic welding that differs from all others in its convenience and speed. Most of the work is not done by a person, but by a machine that feeds the wire evenly and advances the heat source. We are considering the option of using a layer of flux that covers the wire.

What is flux

Flux is a special composition that protects metal from oxidation by air. It is produced in powder, granular, paste and liquid form. Fluxes are fed in large quantities into the weld pool. By displacing oxygen, they create an invisible coating for a reliable seam connection. In addition, fluxes help ensure stable arc burning, do not create large amounts of spatter, and can improve the chemical characteristics of the metal.

Types of fluxes

Before purchasing flux, you should ask about its purpose. They are used for different types of metal:

• for carbon-containing and alloy steels;
• for highly alloyed compounds;
• for non-ferrous alloys.

Based on their composition, fluxes are divided into:

• fused, such fluxes are inexpensive and widely used by welders. Fused flux is a global component in protecting the weld, but nothing more;
• ceramic, if you need enhanced properties of the seam, then choose this type of flux.

And finally, according to their chemical properties, fluxes are:

• active, the mixture contains acids, which can subsequently lead to rust, so carefully knock down the resulting slag;
• passive, such fluxes are not used in automatic mode; their characteristics do not have the necessary properties. The only use of passive fluxes is in soldering, known as rosin or wax.

Which brand of flux to choose is up to everyone to decide for themselves. Russian manufacturers produce inexpensive and good flux, and foreign manufacturers can boast of stable quality. But in both cases, the protective properties of the substances really work. The main thing is to correctly follow the welding technology.

Pros and cons of submerged arc welding

Disadvantages of automatic welding:

• the possibility of welding is limited only to the lower seams;
• it is necessary to more carefully prepare the edges of the products being welded. There is a certain state standard according to which products are cleaned using hardware. After all, automatic mode is a machine that cannot correct or move the edge of the surface;
• high price of equipment and components. But this price is justified, because automatic welding is mainly used on an industrial scale.

A big and fat plus is the absence of the human factor. The master does not need to stand in uncomfortable positions, inhale harmful fumes, control the arc, and, in principle, does not even need to be able to cook. All processes occur automatically. The only thing you need to be well versed in is setting the correct machine settings. The machine will take on the rest of the work, performing the connection at the highest level, both in a single copy and for the millionth series.

The essence of the process

As mentioned above, automatic welding involves more thorough surface preparation. Dust, dirt, grease stains, paint residues, rust and other debris are unacceptable in the technological process. The welding process can only be started on clean and degreased metal.

The automatic process using flux can begin after setting the settings specified by the operator. To set the correct settings, a person must have theoretical knowledge of the welding machine. The thicker the metal, the larger the diameter of the electrode used. At the same time, the welding current and arc voltage increase. But the speed of work decreases with large metal thickness.

On the Internet you can find a lot of calculations when working with different connections. This topic is large-scale and we will not touch on it in this article. We recommend that you study it yourself.

The filler wire used for the flux composition takes part in welding. It would be a good option to choose a rod from the same material from which the welding element itself is made. The additive is supplied automatically; the specialist only needs to fill it into the mechanism.

Flux is poured into a specially designated compartment on the welding machine. Accordingly, flux consumption will be greater when welding thick metals. Any flux melts due to temperature heating, and when it gets onto the weld area, it does not harm its properties, and often improves them. During the welding process, the flux foams and forms metal slag on the joint surface. It needs to be removed.

Welding in automatic mode using flux speeds up the work, but the speed does not affect the quality of the seam.

conclusions

We told you about automated flux welding, but there are both semi-automatic and manual welding using this composition. But we’ll talk about these technologies next time. We ask experienced craftsmen to share their tips and recommendations regarding automatic submerged arc welding.

Source: https://svarka-weld.ru/tekhnologiya-avtomaticheskoj-svarki-pod-flyusom

Submerged arc welding: what is it?

The oxygen environment promotes oxidation of the surface of the workpieces being welded; in addition, when working with some metals and their alloys, additives are required. To protect the weld pool, a special wire is used or the process is carried out in an inert gas environment. They also use a method of welding under a layer of flux, which creates insulation from aggressive oxygen, the absence of pores and cracks in the body of the connecting seam.

Our task is to understand the essence of the process, the composition of the welding flux, the necessary equipment and the equipment that is used.

Process using flux

Manufacturers choose automatic welding under a layer of flux, which is due to considerations of improving the quality of work, and significant savings compared to the argon arc method or semi-automatic feeding of special wire into the melting zone.

The scope of application is very wide and includes a variety of metal welding uses, where there is a flux for forge welding, and there is one for spot or arc welding.

The melting zone is protected by a granular composition, which is selected depending on the workpiece material and is produced by various companies (for example, ESAB).

The sizes of the granules range from 0.2 to 4 mm and are brought into the sphere of action of the short circuit arc, where they melt from high temperature and give the weld the following qualities:

• protect it from exposure to oxygen, creating a slag and gas environment;
• help maintain stable arc action and transfer of electrode metal to the melting zone;
• unnecessary impurities are removed from the body of the weld into the slag formation zone;
• the introduction of flux prevents the formation of pores and cracks, which improves the quality of the connection.

It should be noted that submerged arc welding modes completely depend on the equipment used, the material of the workpieces and the composition of the granules, which may include filler additives. In a separate row there is a flux for forge welding, which helps to connect in the best way and forge metal strips with the required quality.

A method such as automatic submerged arc welding logically dictates the presence of hoppers for granules, which dose the composition into the joint of the future seam and at the same time move in front of the electrode. Such units are controlled remotely by the operator and feed welding wire, which is also an electrode, at a certain speed. This equipment is called submerged arc welding tractor and is uniquely used in industrial production.

It is important that using flux at home requires certain knowledge in this area, since the wrong choice of physical and chemical composition will lead to a noticeable loss of quality.

Types of flux and its technical characteristics

A variety of welding fluxes are used in the fusion of various metals and are involved in various technological processes.

Their physicochemical composition differs depending on the conditions of use, for example, forge welding flux consists mainly of borax, which is melted to remove crystallization water and then crushed to a granular consistency.

Any submerged arc welding requires careful selection of the composition of the granules, which is divided according to the method of its production into unfused and fused.

Unmelted welding fluxes are made by sintering ingredients and contain alloying and deoxidizing impurities, which are either sintered or mixed with liquid glass mass and called ceramic.

The more popular is fused welding flux, which is much cheaper and contains manganese and silicon oxides. Granular compositions for submerged arc welding are offered in a specific range by ESAB.

The oxides are included in the fused form in different proportions and their introduction is due to the welding of non-ferrous metals, special steels for various purposes, alloyed alloys and low-carbon steels.

A special place in submerged arc welding is inherent in the oxygen-free group, which is used when working with rapidly oxidizing alloys and metals. According to the structure of granules, products are divided into glassy and pumice-like types, and according to the degree of alloying into ceramic alloying, and similarly fused low-alloying and passive. According to GOST 9087-81, compositions for submerged arc welding are strictly regulated and are divided, for different groups of metals being welded, into the following types:

1. products for welding low-carbon steels, in these works oxide grades An-65, FC-6, OSTS-45 and FVT-4 are used, they can be used as a flux for forge welding;
2. for alloy steels, products with lower activity FC-16, FVT-1, AN-42 and AN-47 are used;
3. Ceramic flux with metal impurities is used to join a number of steel grades;
4. To work with active metals, oxide-free salt fluxes with a high content of titanium oxide are chosen.

It is very important to select not only the chemical composition of the product, but also the operating mode, as well as the equipment.

The flux, after dosing, is melted in furnaces, and then ground and granulated. After calcination, the products are packaged in bags or tin containers.

Submerged Welding Equipment

To carry out submerged arc welding, you can use both step-down transformers and semi-automatic machines, coordinating the production cycle modes, metal composition and filler product parameters.

The production uses automatic welding with wide functionality in various industries that require mass-produced metal structures. Operator-controlled, self-propelled welding tractors allow a large volume of work to be performed and are used in submerged arc welding.

The TS-12M tractor moves with the help of an electric motor, has a controlled wire feeder and hoppers for flux.

The ADS-1000-2 unit has greater freedom of movement and operating mode adjustments, which are set by the operator according to technical conditions. Thus, the automatic welding machine is equipped with a self-regulating device for changing the wire feed speed, and self-restoring arc current, as well as a function for remote control of the welding current through a transformer.

Automatic or semi-automatic machines consist of the following main components:

• the current source is usually three-phase, powered from a 380 V network;
• control unit with operating mode settings;
• devices for feeding electrode wire with a reel;
• bunkers for supplying flux with compressed air under pressure;
• hose with voltage supply and wire with tip;
• movement mechanism.

In the case of a seam with cutting edges of the surfaces being welded, it is possible to adjust the flux supply to create a reliable welding joint between the parts.

What's the result?

Thus, we talked about what kind of flux can be used for forge welding, as well as the need to select this product as an important component for the automatic welding of metals and their alloys. The use of flux significantly improves the quality of work and reduces the cost of the production process, and the recommendations of GOST standards will not allow you to make serious mistakes.

Source: https://electrod.biz/varim/svarka-pod-sloem-flyusa.html

Automatic submerged arc welding: what it is, where and how it is used, features

Every welding master knows how the oxygen environment affects the seam - not in the most positive way. Once in the area of ​​the base metal that has reached the melting point, it oxidizes the solid metal and various alloys.

There are ways to get rid of this problem. You can treat the metal with antioxidant substances, or you can use auxiliary materials, such as fluxes.

Using flux in combination with automatic equipment is the primary method used by welders. Thanks to “this pair” the seams are smooth and resistant to oxidative corrosion.

Flux helps in welding even “difficult” metals, such as non-ferrous or stainless steel. Automatic equipment does not require much effort from the technician, and the flux itself provides protection for the connection.

In this article we will share the technique of automatic submerged arc welding, describe what it is, and also talk about the pros and cons of this method.

Where is it used?

Automation is used for various purposes. “Self-sufficient” equipment now has its place in every large production, where parts are manufactured in large batches on conveyors.

Automotive assembly, pipeline structures, beams, shipbuilding and other heavy industries thrive thanks to the operation of automatic welding machines and machines.

They are capable of making tight and reliable joints through automatic flux welding, which are highly valued in these fields.

Role

We learned about automatic welding. What is welding flux?

This is a material that protects both the finished product and the metal itself. Thanks to the flux, the heating of the arc becomes more stable, and the connection is protected from the “harmful” influence of atmospheric gases, especially oxygen.

These substances are usually based on fluorides, chlorides or boric acid in the form of granules, powder or even liquids. Substances in the composition must pass electric current, and this rule is the basis for its production.

Kinds

In order not to spoil the welding process and result, you need to take into account the types of fluxes. First of all, the type you choose should depend on the properties of the metal being welded.

A material suitable for welding stainless steel can ruin high-carbon steel and vice versa. Therefore, before purchasing, it is better to consult with a specialist or find compatibility tables.

Most often, fused flux is used for automatic welding. It is sold in the form of small granules and is considered universal for all types of work and metals. However, it should be used when there are no special requirements for the quality and properties of the seam.

If you need to not only protect the welding area from oxygen, but also ultimately obtain the correct connection, use ceramic. It has varieties, among which you can find the one that is needed specifically for your metal.

Also, fluxes can be active or passive. Let us immediately note that passive types are not used for automatic welding, since they cannot fully protect the metal and strengthen the connection.

Active fluxes are acidic, so they must be completely removed from the metal surface at the end of work to avoid corrosion.

Welders often argue about manufacturers on forums and construction markets. Some masters are convinced that there is nothing better than foreign companies. Others, on the contrary, defend the quality of domestic producers.

In practice, both options exist, and their products perform well in operation.

"Pros and cons"

Submerged arc welding process

The main advantage of automatic submerged arc welding lies in its name. The master does not have to study the intricacies of welding to apply this method; it is only important to know how to select materials and set up the machine.

And the absence of “human” errors and incorrect movements in the process guarantees an even, correct seam on any metal.

But it will not always be possible to use such surfacing. Its use does not make it possible to make the upper seams - only the lower ones.

Additionally, the parts you “load” into the machine must be fitted with great precision because the machine is set up to deposit metal in one specified area.

If you miss something when joining elements, the result will be defective. Before fixing the element, you need to melt the base of the structure, fixing it on a horizontal plane. It is impossible to connect metal parts by weight.

The main disadvantage of automatic submerged arc welding is its cost. It is not profitable to buy it for household use only. In addition, these devices often take up a lot of space and use a large amount of electricity.

Conclusion

At high temperatures, flux melts, just like metal. However, its melting will not affect the characteristics of the seam. The only thing it can do is improve them by providing resistance to oxygen and, as a result, oxidation.

However, it is important to remove any remaining substance so that its acid does not corrode the metal. You can use the remainder of the loaded substance again.

Now you know more about submerged arc welding. It is used not only in automatic production plants, but also for manual or semi-automatic welding.

However, each of them has its own characteristics, rules and precautions. We will talk about this in other articles on our website. And in the comments below you can share your knowledge on this topic. Good luck!

Source: https://prosvarku.info/tehnika-svarki/avtomaticheskaya-svarka-pod-flyusom